Method of detecting washing machine unbalance and operation control method using the same

ABSTRACT

A method of detecting a dewatering unbalance of a washing machine and an operation control method using the same is provided, by which a system stability on dewatering is enhanced by controlling a dewatering speed to be appropriate for a state of unbalance that is quickly and accurately detected at an early stage of the dewatering. In a washing machine sequentially performing washing, rinsing, draining, and dewatering on a washing tub holding water and laundry therein, a method of detecting a dewatering unbalance of the washing machine, including a step of detecting an unbalance amount through a variation width of a rotational speed of the washing tub on performing the dewatering.

[0001] This application claims the benefit of Korean Application No. 10-2002-0085805 filed on Dec. 28, 2002, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a washing machine, and more particularly, to a method of detecting a dewatering unbalance of a washing machine and an operation control method using the same, by which a system stability on dewatering is enhanced by controlling a dewatering speed to be appropriate for a state of unbalance that is quickly and accurately detected at an early stage of the dewatering.

[0004] 2. Discussion of the Related Art

[0005] Generally speaking, a washing machine is an apparatus for cleaning an object such as laundry and typically employs a washing tub in which the laundry and a predetermined amount of water is rotated under the control of a microcomputer using an algorithm set according to a selected wash course to perform in sequence washing, rinsing, draining, and dewatering steps. The washing tub is driven at a predetermined speed for each step. A contemporary washing machine may use any one of several drive and control techniques for rotating the washing tub to perform the above steps, including transferring a rotational force via a belt-and-pulley linkage to a dewatering shaft to rotate the tub,

[0006] transferring a rotational force via a belt-and-pulley linkage to a washing shaft to rotate a pulsator or drum, controlling the speed of a BLDC motor, to rotate the tub at two different speeds (for washing and dewatering), separately controlling a power transfer path of a BLDC motor, to rotate a pulsator at a first speed (for washing) and rotating the pulsator and tub at a second speed (for dewatering), and performing “penetration” washing, by pumping a current of water into the tub while rotating the tub or wash vanes.

[0007] Referring to FIG. 1, illustrating a general washing machine, in which washing and dewatering are performed by a rotational speed control of a brushless DC (BLDC) motor, an outer tub 2 is installed within an outer case 1 to be supported by a suspender 7, and an inner tub 3 is rotatably installed within the outer tub 2. A pulsator 4 is installed at an inner bottom of the inner tub 3, and a motor 5 is provided to one side under the outer tub 2 to transfer a drive force to the inner tub. A water level sensor 9 is provided to a predetermined portion of the top cover 12 and may be a mechanical device or a semiconductor device. A pressure transfer tube 10 is connected between the water level sensor 9 and the outer tub 2 to transfer an air pressure according to a water level of the outer tub. A fluid balancer 20 holding salt water inside is provided to an upper inside of the inner tub 3 to reduce an unbalance of the washing tub by fluid flow.

[0008] In the above-constructed washing machine according to the related art, when laundry and detergent are put in the inner tub 3 to be ready for washing, a washing start button is pressed. After a laundry amount is sensed, water supply is executed according to a control signal of the microcomputer. Washing, rinsing, draining, and dewatering are automatically executed in turn, each for a predetermined time.

[0009] At the time of dewatering execution, however, the laundry is likely to be entangled, producing an excessive eccentricity, such that the outer tub 2 hits a sidewall of the outer case, known as “striking,” which generates an associated noise and vibration to degrade system stability and reliance. Meanwhile, in determining a dewatering rotational speed of dewatering, the unbalance on dewatering is detected so that the dewatering is performed at the rotational speed appropriate for the detected unbalance amount. Yet, the related art unbalance detector is very sensitive to a mechanical influence, and as a result, its accuracy is unreliable.

SUMMARY OF THE INVENTION

[0010] Accordingly, the present invention is directed to a method of detecting a dewatering unbalance of a washing machine and an operation control method using the same that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.

[0011] An object of the present invention, which has been devised to solve the foregoing problem, lies in providing a method of detecting a dewatering unbalance of a washing machine and operation control method thereof, by which a system stability on dewatering is enhanced by controlling a dewatering speed to be appropriate for a state of unbalance that is quickly and accurately detected at an early stage of the dewatering.

[0012] Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent to those having ordinary skill in the art upon examination of the following or may be learned from a practice of the invention. The objectives and other advantages of the invention will be realized and attained by the subject matter particularly pointed out in the specification and claims hereof as well as in the appended drawings.

[0013] To achieve these objects and other advantages in accordance with the present invention, as embodied and broadly described herein, there is provided, in a washing machine sequentially performing washing, rinsing, draining, and dewatering on a washing tub holding water and laundry therein, a method of detecting a dewatering unbalance of the washing machine, comprising a step of detecting an unbalance amount through a variation width of a rotational speed of the washing tub on performing the dewatering.

[0014] In another aspect of the present invention, there is provided, in a washing machine sequentially performing washing, rinsing, draining, and dewatering on a washing tub holding water and laundry therein, an operation control method of the washing machine, comprising steps of detecting an unbalance amount through a variation width of a rotational speed of the washing tub on entering the dewatering; and performing the dewatering at a rotational speed appropriate for the detected unbalance amount.

[0015] In another aspect of the present invention, there is provided, an detecting an unbalance amount through a variation width of a rotational speed of a washing tub of a washing machine on performing dewatering, the washing machine sequentially performing washing, rinsing, draining, and the dewatering on the washing tub holding water and laundry therein, a method of detecting a dewatering unbalance of the washing machine, comprising steps of detecting the variation width of the rotational speed of the washing tub from a steady rotational speed section among a first resonance RPM band; if RPM is reduced by more than a predetermined amount, generating an error-induction possible signal; if the error-induction possible signal is generated, detecting an RPM value per unit time within a predetermined time range from a moment of the generation of the error signal; and finding an unbalance determination value using root mean square based on the detected RPM values.

[0016] It is to be understood that both the foregoing explanation and the following detailed description of the present invention are exemplary and illustrative and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

[0018]FIG. 1 is a cross-sectional view of a general washing machine;

[0019]FIG. 2 is a graph of dewatering time versus washing tub speed;

[0020]FIG. 3A is a graph of washing tub speed according to the present invention, showing an unbalance amount on acceleration;

[0021]FIG. 3B is a graph of washing tub speed according to the present invention, showing an unbalance amount at steady rotational speed;

[0022]FIG. 4 is a graph of a relation between an unbalance amount and an unbalance determination value; and

[0023]FIG. 5 is a graph of a method of detecting unbalance according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[0025]FIG. 2 is a graph of dewatering time versus washing tub speed; FIG. 3A is a graph of washing tub speed according to the present invention, showing an unbalance amount on acceleration; and FIG. 3B is a graph of washing tub speed according to the present invention, showing an unbalance amount at steady rotational speed.

[0026] In a washing machine sequentially performing washing, rinsing, draining, and dewatering for a predetermined time after completion of laundry input and water supply to a washing tub, the present invention detects an unbalance amount through a variation width of a rotational speed of the washing tub at an early stage of entering the dewatering.

[0027] In doing so, the variation width of the rotational speed of the washing tub is preferably detected from a first resonance RPM band. More preferably, the variation width is detected from a steady rotational speed section among the first resonance RPM band.

[0028] A method of controlling dewatering according to the present invention is explained in detail as follows.

[0029] First of all, when laundry and detergent are put in the washing tub 3 to be ready for washing, a washing start button is pressed. After a laundry amount is sensed, water supply is executed according to a control signal of the microcomputer. Washing, rinsing, draining, and dewatering are automatically executed in turn, each for a predetermined time.

[0030] In doing so, in an operation control method of a washing machine according to the present invention, an unbalance amount is detected through a variation width of a rotational speed of a washing tub at an early stage of entering the dewatering and the dewatering is then executed at the rotational speed appropriate for the detected unbalance amount.

[0031] Namely, the variation width of the washing tub is detected from the steady rotational speed section within the first resonance RPM band according to the above-described unbalance detection method, and the corresponding dewatering rotational speed is determined to belong to one of a normal rotational speed section, an intermediate rotational speed section, and a minimum rotational speed section, according to a range to which the detected unbalance amount belongs.

[0032] For instance, if the range to which the detected unbalance amount belongs is a normal range, e.g., 0˜1.35 kg, the dewatering is performed at the normal dewatering rotational speed. If the range to which the detected unbalance amount belongs is an intermediate range, e.g., 1.35˜2.5 kg, the dewatering is performed at a dewatering rotational speed which is lower than the normal rotational speed but higher than the minimum rotational speed. If the range to which the detected unbalance amount belongs is a maximum range, e.g., over 2.5 kg, the dewatering is performed at the minimum rotational speed.

[0033] Thus, the watering can be executed despite the unbalance at the early stage of entering the dewatering.

[0034]FIG. 4 is a graph of a relation between an unbalance amount and an unbalance determination value.

[0035] Referring to FIG. 4, the unbalance amount detected by the above-described method according to the present invention exhibits no substantial difference of a determination value in a low section (0˜0.6 kg) to have low discrimination but exhibits a great difference of the determination value in a section having a big unbalance amount (0.6˜2.3 kg) to have high discrimination.

[0036] Hence, the above-explained method according to the present invention is useful to detect the unbalance amount of the section (1.35 kg˜2.5 kg) requiring accuracy for a dewatering rotational speed control.

[0037]FIG. 5 is a graph of a method of detecting unbalance according to another embodiment of the present invention.

[0038] Referring to FIG. 5, in a method of detecting unbalance according to another embodiment of the present invention, a variation width of a rotational speed of a washing tub is detected from a steady rotational speed section among a first resonance RPM band. If the speed of the washing tub is reduced by more than a predetermined amount, e.g., 0.5 rpm, an error-induction possible signal is generated. Thereafter, if an error signal having the RPM reduced further to a predetermined size is generated, an RPM value is detected per unit time (1 msec) within a predetermined time range from the moment of the generation of the error signal. An unbalance determination value is found by root mean square based on the detected RPM values.

[0039] Namely, a detection start point is a time point of R(n)□R(n□1) □0.5 rpm, and the unbalance determination value (UB) is found by the following equation. ${UB} = {\overset{15}{\underset{i - 1}{Q}}{{{{Pi} - X}}}}$

[0040] Here, X is an average of P1˜P15.

[0041] Hence, by the above method according to the embodiment of the present invention, the unbalance value on entering the dewatering is determined. The dewatering rotational speed can be controlled according to the determined unbalance value.

[0042] Specifically, in such a case, the unbalance amount can be determined in a very short time in detecting the unbalance, and a variation tendency of the determination value can be predicted through the comparison of the periodically computed determination values. Hence, if it is predicted that the unbalance amount is to increase according to the variation tendency of the determination value, the operation of the washing machine is stopped, to prevent striking.

[0043] Accordingly, the present invention controls the dewatering rotational speed to be appropriate for a state of unbalance that is quickly and accurately detected at an early stage of entering the dewatering, thereby enabling to enhance the system stability on dewatering.

[0044] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover such modifications and variations, provided they come within the scope of the appended claims and their equivalents. 

What is claimed is:
 1. In a washing machine sequentially performing washing, rinsing, draining, and dewatering on a washing tub holding water and laundry therein, a method of detecting a dewatering unbalance of the washing machine, comprising a step of detecting an unbalance amount through a variation width of a rotational speed of the washing tub on performing the dewatering.
 2. The method as claimed in claim 1, wherein the variation width of the rotational speed of the washing tub is detected from a first resonance RPM band.
 3. The method as claimed in claim 2, herein the variation width of the rotational speed of the washing tub is detected from a steady rotational speed section.
 4. In a washing machine sequentially performing washing, rinsing, draining, and dewatering on a washing tub holding water and laundry therein, an operation control method of the washing machine, comprising steps of: detecting an unbalance amount through a variation width of a rotational speed of the washing tub on entering the dewatering; and performing the dewatering at a rotational speed appropriate for the detected unbalance amount.
 5. The method as claimed in claim 4, wherein the variation width of the rotational speed of the washing tub is detected from a first resonance RPM band.
 6. The method as claimed in claim 5, herein the variation width of the rotational speed of the washing tub is detected from a steady rotational speed section.
 7. The method as claimed in claim 5, wherein the rotational speed of the dewatering is determined to belong to one of a normal rotational speed section, an intermediate rotational speed section, and a minimum rotational speed section, according to a range to which the detected unbalance amount belongs.
 8. In detecting an unbalance amount through a variation width of a rotational speed of a washing tub of a washing machine on performing dewatering, the washing machine sequentially performing washing, rinsing, draining, and the dewatering on the washing tub holding water and laundry therein, a method of detecting a dewatering unbalance of the washing machine, comprising steps of: detecting the variation width of the rotational speed of the washing tub from a steady rotational speed section among a first resonance RPM band; if RPM is reduced by more than a predetermined amount, generating an error-induction possible signal; if the error-induction possible signal is generated, detecting an RPM value per unit time within a predetermined time range from a moment of the generation of the error signal; and finding an unbalance determination value using root mean square based on the detected RPM values. 